Most commercial aircraft are equipped with temperature probes that are used to measure external (e.g., ambient) total air temperature. These aircraft total air temperature (TAT) probes are typically mounted on an aircraft body or in an engine inlet. The temperatures supplied from TAT probes mounted on an aircraft body are often used in the calculation of airspeed. The temperatures supplied from TAT probes mounted in an engine inlet are often used in engine power setting, guide vane scheduling, and surge bleed (handling) valve scheduling. Thus, accurate TAT measurement can be important.
The TAT probes, whether mounted on the aircraft or in an engine inlet, are subject to icing. The TAT probes, when iced, can misreport the true total air temperature. Thus, many TAT probes include a heating feature to inhibit such icing. Although the heating feature can adversely impact the reported temperature, the impact can be minimized via known compensating algorithms. Even so, the heating feature may not guarantee ice free operation of the TAT probes, particularly when operating in an environment containing ice crystals. Moreover, enablement of the heating feature is typically a pilot action. Should the pilot not enable the heating feature in a timely manner, the TAT probes can become iced, and the misreport the true total air temperature. In addition, the process of probe icing is sufficiently slow that it can go undetected.
Hence, there is a need for a system and method of determining total air temperature without relying on TAT probes that are mounted on the aircraft and/or in an engine inlet. The present disclosure addresses at least this need.